Revamped concurrency API

[Tim Matthews]

Andrei Alexandrescu wrote:

> 
> Speaking of switch, I have tried to convince Walter to require either a 
> break; or a goto case xxx; at the end of each snippet inside a switch. I 
> was surprised by his answer: "but I use fall through all the time!" :o)
> 
> I personally think requiring a goto case xxx; is more robust in presence 
> of code maintenance because its semantics is invariant to code moves.
> 
> 
> Andrei

First of all goto case is without a doubt safer and more robust but 
please leave as much of D as possible to remain compatible with C.

Since D has objects a lot of code can be polymorphic through the 
classes/interfaces that C didn't have.

C's design is trust the programmer, provide full power. It is unsafe 
agreed but by design. Breaking compatibility between D1, D2 etc may be 
an issue but if you loose the C then you lose what defines D.